What i like to do is go off by myself or take at the most one person wiht me and make a wide flanking move to get around to their backs. granted ODDLES of players anticipate this but when i (or when anyone performing this flanking move) decide to pull this manuver there is really little one can do to stop it. it is KEY though to let the rest of your team play as per usual, that way the enemy wont think anything is up untill you're up on their blindside and have them trapped in a crossfire.
Another thing i like to do is take risks. i'll have two players (who use automatic long range guns) lay down a base of fire and i will move up under it as close as possible. anyway the basis of this is laying down a steady base of fire then moving your team up. works like a charm.
Mess with the best, Die like the rest
This is my Rifle. There are many like it but this one is mine......